Systems for automatic control of a prime mover torque in certain states of operation of vehicles are basically known.
In many vehicles having stepped automatic transmission, a so-called "motor gearing" is used during traction upshifts in order to compensate for the acceleration excess resulting from the rotary mass being decelerated during the gearshift operation. A desired effect is also the reduction of friction in shifting clutches involved.
Also known are different systems for preventing clutch overloads during gearshifts. It is usual, for example, in vehicles with automatic transmissions that, during the gear change from "N" to a driving step "D" or "R", motor power, motor torque or the motor speed are limited.
These systems have in common that the prime mover torque becomes reduced for a brief time during certain shifting operations.
There have further become known methods for operating a driving unit in which the prime mover power is limited in accordance with certain transmission ratios. Such a driving device has been described, for example, in DE OS 3735246. In this known driving device the motor capacity is limited briefly in a reverse gear in order that the transmission does not have to be (over) dimensioned for this load situation. The limitation of the motor capacity is here firmly linked to the condition that a certain gear (reverse gear) be engaged.
Electronic idling speed controls are likewise related to the instant invention. But in such systems it is essential that the systems be tailored to the idling range (load position "0"). Control is here based on a preset idling speed. A consuming device to be engaged as a rule leads to a speed drop until a control reacts to this.
In many manufactured driving units with a transmission having variable (stepped or continuous) ratios for adaptation to different vehicle speeds, additional consuming devices are directly or indirectly driven by the prime mover. The torque flow to such added consuming devices often is not constant and its magnitude can change depending on the shifting or operating state.
First of all, when the torque flow to the added consuming device can assume relatively high values, the driving performance (speed and acceleration) becomes impaired. Specially in tracked vehicles, a steering transmission, when cornering, can be an added consuming device using substantial portions of the prime mover torque so that the effect on the driving performance is considerable. An cross-drive steering transmission with integrated transmission and steering transmission parts is the object of DE 38 33 784.